The invention relates to an open end friction spinning machine with a plurality of spinning units which respectively include two adjacently arranged friction rollers drivable in the same rotational direction and forming a yarn forming wedge-shaped gap therebetween. In this gap, yarn is spun with the assistance of a friction effect on the fibers guided thereto. The friction effect is created with the assistance of the outer surfaces of the rollers in conjunction with a suction air stream in the wedge-shaped gap formed by a suction device.
Practical tests have shown that with spinning units for open end friction spinning, which for example are constructed according to DE-PS No. 24 49 583, difficulties are encountered in maintaining the quality of the spun yarn over a long period of time in spite of careful adjustment of the spinning units. This quality deviation occurs at an individual spinning unit and also between several spinning units which had been previously adjusted to the same values.
An objective of the present invention is the provision of an open end friction spinning machine of the above-mentioned kind wherein the causes for a variation in yarn quality is determined.
Another objective of the present invention is the provision of an open-end friction spinning machine capable of initiating counter measures for eliminating variation in yarn quality after determination of the causes thereof.
These and other objectives of the present invention are attained in the provision of means for determining the portion of the friction effect attributable to the outer surfaces of the rollers without having these means alter the friction effect.
The invention is based upon the recognition that the primary reasons for quality changes in the spun yarn are changes in the friction effect, which then immediately lead to a change in the yarn quality and the yarn structure. According to the invention, it is possible to examine an essential characteristic upon which the friction effect is based. This essential characteristic is the portion of the friction effect which is affected by the outer surface structure of the rollers.
According to a preferred embodiment of the invention, there is provided a disturbance free functioning sensor for examining the outer surface structure of the examined roller and providing a signal representative thereof. Through the disturbance free functioning there results the advantage that the sensor itself causes no alteration such as abrasion and thereby also does not contribute to changes in the examining effectiveness. The resulting signal is thereby only dependent upon the respective occurring surface structure of the examined roller. Thereby it is especially advantageous to provide an optical sensor, preferably one constructed to be responsive to scattered light. This kind of sensor can be installed with success and can be manufactured today for the examination of the roller surface characteristics.
In further features of the invention, it is provided that the sensor is connected to an evaluating device for receiving signals representing the portion of the friction effect depending upon the surface of the examined rollers. In this case, it is possible not only to determine the respective occurring surface structure but also to evaluate the same qualitatively and determine exemplary permissive tolerance ranges.
In further developments of the invention, the sensor and/or the evaluating device are arranged in a travelling maintenance unit adjustably movable relative to respective spinning units. Thereby it is possible to undertake a relatively high expense for examination of the surfaces of the rollers and determination of the corresponding friction effect, without undue influencing of the economics of the entire machine. This is so because the servicing or maintenance unit can be used for a plurality of spinning units. Thereby it is advantageous if the maintenance unit is outfitted with means for adjusting the sensors to at least one of the rollers of a spinning unit. These means for adjusting the sensors are advantageously so constructed that they are adjustable to respectively several positions of a roller so that the overall surface structure of the roller can be examined over a large area. The received signal and evaluation are thereby statistically reliable. It is especially advantageous according to a further development of the invention that the maintenance unit be provided with means for controlling the drive of the rollers. Thereby, it is possible to examine the outer surface structure of the rollers over a portion of the circumference. Accordingly, a statistically reliable measurement can be determined. If a common drive is provided for the rollers of several spinning units, the means for controlling the drive of the rollers can then include means for individually stopping and driving the rollers, which can in any event be also combined with brakes. If individual drives for the rollers of the individual spinning units are provided, then the means for stopping and controlling the rollers can include a control device for the individual drives so that they can adjust them for the examination of the cover surface structure with the preferred rotational speeds.
In further developments of the invention it is provided that the maintenance unit is outfitted with means controlled by the evaluation device for stopping and/or marking an examined spinning unit. The maintenance unit thereby stops a spinning unit which is not error free or so marks the same such that a servicing person knows that a servicing process should be carried out on the spinning unit in order to obtain the desired yarn quality. The marking is so selected that it simultaneously shows the servicing person in which manner an adjustment should be carried out, i.e., whether an increase or decrease in the entire friction effect is needed.
In further developments of the invention it is provided that each spinning unit is outfitted with means for adjusting the strength of the suction effect of the suction device acting at the wedge-shaped gap. The servicing person then undertakes an adjustment of the strength of the suction effect in dependence upon the determined deviation and corresponding to the outer surface of the rollers of a spinning unit in order to achieve again a desired overall friction effect for the required quality. Insofar as an individual drive for the rollers of the spinning unit is provided the servicing person also adjusts the rotational speed of the rollers in dependence upon the determined value of the outer surface structure of the rollers.
In further developments in the invention, it is provided that the maintenance unit is outfitted with means guided by the evaluating device for the adjustment of the means for regulating the strength of the suction effect at a spinning unit. Thereby the adjustment of the portion ascertained for the friction effect is automatically carried out. If individual drives for the rollers are provided at the spinning unit, a regulation of the rotational speed for the rollers can be carried out in a corresponding manner auxiliary to the adjustment of the strength of the suction effect or also in place of such adjustment.
In order to facilitate a quantitative adjustment of the overall friction effect with the maintenance device it is provided in further developments of the invention that the maintenance device is connected with means for examining the strength of the suction effect of the suction device of a spinning unit. This means can for example be an examining head which is adjustably movable to the region of the wedge-shaped gap of the rollers which can detect the air flow occurring under pressure and/or the strength of the suction air stream. However, the means can also be formed as a connecting piece connected with a detector that is adjustable to a corresponding connecting piece of the suction device of a spinning unit and which measures the magnitude of the vacuum occurring in the suction device. In a corresponding manner it is also possible to provide the maintenance device with a device for determining the rotational speed of the rollers, especially if an individual drive for the rollers of a spinning unit is provided. Also, the evaluating device of the maintenance unit can be so constructed that the maintenance unit can undertake a test for adjusting the desired friction effect. Only if this adjustment is not feasible because of the adjustment possibilities provided would the corresponding spinning unit be marked and/or shut down so that it is only brought back into operation after elimination of the determined disturbance of the friction effect.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.